US4020350A - Isotope selective excitation and separation method and apparatus utilizing circularly polarized pulsed radiation - Google Patents

Isotope selective excitation and separation method and apparatus utilizing circularly polarized pulsed radiation Download PDF

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Publication number
US4020350A
US4020350A US05/589,168 US58916875A US4020350A US 4020350 A US4020350 A US 4020350A US 58916875 A US58916875 A US 58916875A US 4020350 A US4020350 A US 4020350A
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radiation
molecules
atoms
energy level
laser
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Theodore W. Ducas
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Massachusetts Institute of Technology
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Massachusetts Institute of Technology
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Priority to GB25314/76A priority patent/GB1534909A/en
Priority to CA255,425A priority patent/CA1061476A/en
Priority to FR7619004A priority patent/FR2315310A1/fr
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D59/00—Separation of different isotopes of the same chemical element
    • B01D59/34—Separation by photochemical methods

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  • This invention relates to apparatus and method of separation of different isotopes of the same element in a simple and efficient manner.
  • Another suggested method using lasers involves deflection of one isotope vs. another in an atomic or molecular beam using the momentum transfer from resonantly absorbed laser light. Again, these techniques require a very narrow-banded laser, good stability, and, in addition, an atomic beam apparatus which generally means a lower density of atoms than, say, a gas cell.
  • FIG. 1(a) shows schematically a system of sublevels in the (I,J,F,M f ) representation.
  • FIG. 1(b) gives the same levels as in FIG. 1(a) in the degenerate (I,J,M I ,M J ) representation.
  • FIG. 2(a) is a block design representation of a preferred embodiment of this invention.
  • FIG. 2(b) is a detailed drawing of the variable delay unit of FIG. 2(a).
  • FIG. 2(c) is a timing diagram showing the sequence of laser pulses and electric field pulse.
  • FIG. 3(a) shows schematically a system of sublevels in the (I,J,F,M f ) representation for relevant sodium energy levels.
  • FIG. 3(b) shows the same levels as in FIG. 3(a) in the degenerate (I,J,M I ,M J ) representation.
  • the central aspect of the invention is the successive excitation of the atoms or molecules by two pulsed lasers having the same sense or handedness of circular polarization.
  • the first laser pulse creates a coherent superposition state in an intermediate level.
  • the second laser pulse serves to excite selectively atoms or molecules prepared in this superposition state to a higher level.
  • the critical conceptual aspect of this technique centers around the first step -- creation of the coherent superposition state. Therefore, a detailed description of this step is useful.
  • FIG. 1(a) shows schematically a particular system of sublevels in the (I,J,F,M f ) representation. Levels a and b are split ⁇ by the hyperfine interaction. Laser 1 of FIG. 2 excites a coherent superposition from level g to levels a and b; laser 2 causes transitions from this superposition to a higher level k.
  • each photon has Fourier frequency components over a frequency range larger than ⁇ and it creates an excited state that is a coherent superposition of states a and b.
  • the center frequency of the laser should be within 2 ⁇ / ⁇ t of the frequencies corresponding to the energy differences of the average energy of a and b.
  • the Fourier power spectrum is centered about the frequency separation of the levels to be excited.
  • the center frequency of the laser is not critical and it is apparent that photons centered about frequencies greater than 2 ⁇ / ⁇ t can still contribute to creating coherent superposition states of a and b because of the wide spectrum of a short pulse.
  • FIG. 1(b) gives the same levels in the degenerate (I,J,M I ,M J ) representation.
  • the incoming photons are right-hand circularly polarized and thus each must cause M J to increase by one.
  • the intermediate state has some "V 1 -like" character.
  • the states are described by the principal quantum number n and the quantum numbers I, J, F and m F , where the latter corresponds to the projection of F onto a particular axis in space, F z .
  • the only excitation between the lower level and the intermediate level occurs between U 1 and V 2 .
  • m I m" F +1/2
  • m j m F " +1/2.
  • This laser excitation can take place in an atomic (or molecular) beam or a gas cell.
  • the latter permits higher densities of atoms (or molecules).
  • the only restriction on a cell are the destruction of high-lying states by collisions--this should only begin to be important at higher pressures than typical in atomic beams.
  • FIG. 3 shows the relevant sodium energy-levels in the F representation (FIG. 3(a)) and schematically in the degenerate representation (FIG. 3(b)).
  • Theoretical understanding of this real case lies in realizing that it consists of several g ⁇ a,b, ⁇ k sublevels systems as discussed above and as shown in FIG. 1.
  • g's are sublevels of the 3s 1/2 ground state
  • the resonance oscillation method has been described for the case of one isotope having structure while the other isotope doesn't.
  • the method is more general and can be used to separate isotopes even if both have structure.
  • the splitting of one isotope ( ⁇ 1 ) is almost always different from that of another ( ⁇ 2 ).
  • the time of application of the second laser pulse can be adjusted for maximum excitation of just one isotope.
  • t ⁇ / ⁇ 2 .
  • selectivity in excitation occurs because the optimal excitation time for one isotope differs from that of the other -- and thus they are excited to the highest state with different probabilities.
  • the desired isotope can either be the one selectively excited and swept out by an ion collector or the one remaining in the interaction region.
  • FIG. 2 illustrates a preferred embodiment of the invention.
  • Lasers 1 and 2 are pumped by the same laser 3 -- as for example two tunable pulsed dye lasers 1, 2 pumped by the same pulsed nitrogen laser 3.
  • the output of laser 3 is divided in beam splitter 8.
  • One beam 9 pumps laser 1.
  • the other beam 10 is reflected by mirror 11 before pumping laser 2.
  • Laser 2 is delayed in a variable delay unit 4 with respect to laser 1 by bouncing off movable mirrors 5, 6 of variable separation as shown by direction arrows 7 in FIG. 2(b).
  • Mirror 12 reflects the beam of laser 1 into variable delay unit 4 where it is merely redirected by mirror 13 to impinge upon the atoms or molecules 14 in chamber 15.
  • the output of laser 1 and 2 are circularly polarized by polarizer 16.
  • the polarizer 16 may be either right or left hand polarizers so long as both are the same.
  • the laser 3 is triggered in a conventional manner by a pulse source 17 which produces a continuous train of pulses.
  • the delayed pulse triggers a pulsed voltage source 20 which provides an ionizing voltage +V between plates 21, 22.
  • the space between these plates 21, 22 contains a gas which has been energized by lasers 1, 2.
  • the ions are also given an acceleration toward plate 22 by the ionizing voltage so that they pass through the screen 23 which forms a major portion of plate 22.
  • An ion collector 18 connected to a negative voltage source 24 collects the ion which pass through the screen 23 to provide substantially only one isotope at output 25 whereas the remainder of the gas exits at output 26.
  • Enclosure 15 is provided with input gas at input 27.
  • FIG. 2(c) shows the timing sequence of the laser pulses and the ionizing electric field pulse.
  • the ionizing electric field pulse preferably closely follows the pulse from laser 2 in order to minimize the period and hence allow a higher repetition rate.
  • the ion creating electric field is a pulsed source which was energized after the second laser radiation was terminated
  • an alternate embodiment of the invention is one in which the electric field is continuously applied.
  • the ionization voltage produces a change in the frequency separation of the levels and causes additional energy levels. The perturbations in the energy levels of the gas because of the continuously applied ionizing field can be avoided if the pulsed ionizing field is applied after the second laser pulse since there are no perturbations in the absence of the ionizing field.
  • the two lasers may be replaced by only one laser whose circularly polarized beam is split in a beam splitter to provide two beams corresponding to the beams from lasers 1 and 2.
  • One beam, corresponding to that of laser 2 is delayed in variable delay unit 4 of FIG. 2.
  • the apparatus otherwise is the same as that of FIG. 2.

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  • Life Sciences & Earth Sciences (AREA)
  • Biophysics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Lasers (AREA)
  • Extraction Or Liquid Replacement (AREA)
US05/589,168 1975-06-23 1975-06-23 Isotope selective excitation and separation method and apparatus utilizing circularly polarized pulsed radiation Expired - Lifetime US4020350A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US05/589,168 US4020350A (en) 1975-06-23 1975-06-23 Isotope selective excitation and separation method and apparatus utilizing circularly polarized pulsed radiation
GB25314/76A GB1534909A (en) 1975-06-23 1976-06-18 Selective excitation of atoms or molecules to high-lying states
CA255,425A CA1061476A (en) 1975-06-23 1976-06-22 Selective excitation of atoms or molecules to high-lying states
FR7619004A FR2315310A1 (fr) 1975-06-23 1976-06-22 Procede et appareil d'excitation selective et de separation d'isotopes

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CA (1) CA1061476A (ref)
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GB (1) GB1534909A (ref)

Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4097384A (en) * 1976-03-22 1978-06-27 Northwestern University Process for uranium isotope separation
US4138297A (en) * 1976-03-05 1979-02-06 Kraftwerk Union Aktiengesellschaft Method for isotope separation by means of coherent electromagnetic radiation
US4142955A (en) * 1977-09-14 1979-03-06 Calspan Corporation Method for the initiation of chemical reactions by low pressure optical pumping
US4158589A (en) * 1977-12-30 1979-06-19 International Business Machines Corporation Negative ion extractor for a plasma etching apparatus
US4199679A (en) * 1975-11-27 1980-04-22 Ami Rav Aviv Method and apparatus for the separation of isotopes
US4293769A (en) * 1978-01-13 1981-10-06 Massachusetts Institute Of Technology Detecting IR and mm radiation
US4490225A (en) * 1982-09-07 1984-12-25 Westinghouse Electric Corp. Separation of isotopes of zirconium
US4496445A (en) * 1982-09-07 1985-01-29 Westinghouse Electric Corp. Separation of isotopes of zirconium
US4526664A (en) * 1974-04-01 1985-07-02 The United Sates Of America As Represented By The United States Department Of Energy Isotope separation apparatus and method
US4568436A (en) * 1982-08-25 1986-02-04 Westinghouse Electric Corp. Separation of isotopes of zirconium
US4634864A (en) * 1983-10-27 1987-01-06 Atom Sciences, Inc. Ultrasensitive method for measuring isotope abundance ratios
US4654183A (en) * 1984-02-13 1987-03-31 The United States Of America As Represented By The United States Department Of Energy Production of intense negative hydrogen beams with polarized nuclei by selective neutralization of negative ions
US4704197A (en) * 1986-11-13 1987-11-03 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Isotope separation using tuned laser and electron beam
US4734579A (en) * 1983-10-27 1988-03-29 Atom Sciences, Inc. Ultrasensitive method for measuring isotope abundance ratios
US4786478A (en) * 1984-07-26 1988-11-22 Conoco Inc. Method and apparatus for isotope separation
US4893019A (en) * 1987-05-27 1990-01-09 Mitsubishi Denki Kabushiki Kaisha Ion current generator system for thin film formation, ion implantation, etching and sputtering
US5011584A (en) * 1988-09-01 1991-04-30 Ultra-Centrifuge Nederland N.V. Method for separating a predetermined isotope of an element from a gaseous compound containing said element
US5110562A (en) * 1989-08-04 1992-05-05 Doryokuro Kakunenryo Kaihatsu Jigyodan Laser isotope separation apparatus
US5115135A (en) * 1989-04-21 1992-05-19 Mitsubishi Denki Kabushiki Kaisha Ion source
WO1993003826A1 (en) * 1991-08-14 1993-03-04 United States Department Of Energy Gadolinium photoionization process
WO1997012373A3 (en) * 1995-09-15 1997-05-09 British Nuclear Fuels Plc Method and apparatus for laser separation of molecular compounds
WO2002014938A1 (en) * 2000-08-15 2002-02-21 Accelight Investments, Inc. High speed polarization mode dispersion compensator
WO2008122205A1 (fr) * 2007-04-06 2008-10-16 Peking University Procédé pour accélérer des ions au moyen d'un laser et appareil pour générer des ions
WO2016109842A1 (en) * 2015-01-02 2016-07-07 Board Of Regents Efficiently ionizing atoms based on electron excitation
US11307129B2 (en) 2020-03-23 2022-04-19 Savannah River Nuclear Solutions, Llc Automatic gas sorption apparatus and method

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69010480T2 (de) * 1990-02-28 1995-01-26 Doryokuro Kakunenryo Vorrichtung zur Laserisotopentrennung.
US5316635A (en) * 1992-05-22 1994-05-31 Atomic Energy Of Canada Limited/Energie Atomique Du Canada Limitee Zirconium isotope separation using tuned laser beams
US5330073A (en) * 1993-04-15 1994-07-19 Boston Advanced Technologies, Inc. Gasoline dispenser leak detectors and automatic shut-off systems
US5422495A (en) * 1993-04-15 1995-06-06 Boston Advanced Technologies, Inc. Optical sensor having a floatation means for detecting fluids through refractive index measurement
US5527437A (en) * 1994-08-19 1996-06-18 Atomic Energy Of Canada Limited/Energie Atomique Du Canada Limitee Selective two-color resonant ionization of zirconium-91

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2312194A1 (de) * 1972-03-19 1973-10-04 Isaiah Nebenzahl Verfahren zur isotopentrennung
US3772519A (en) * 1970-03-25 1973-11-13 Jersey Nuclear Avco Isotopes Method of and apparatus for the separation of isotopes

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2311584A1 (de) * 1973-03-08 1975-04-30 Siemens Ag Trennverfahren

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3772519A (en) * 1970-03-25 1973-11-13 Jersey Nuclear Avco Isotopes Method of and apparatus for the separation of isotopes
DE2312194A1 (de) * 1972-03-19 1973-10-04 Isaiah Nebenzahl Verfahren zur isotopentrennung

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4526664A (en) * 1974-04-01 1985-07-02 The United Sates Of America As Represented By The United States Department Of Energy Isotope separation apparatus and method
US4199679A (en) * 1975-11-27 1980-04-22 Ami Rav Aviv Method and apparatus for the separation of isotopes
US4138297A (en) * 1976-03-05 1979-02-06 Kraftwerk Union Aktiengesellschaft Method for isotope separation by means of coherent electromagnetic radiation
US4097384A (en) * 1976-03-22 1978-06-27 Northwestern University Process for uranium isotope separation
US4142955A (en) * 1977-09-14 1979-03-06 Calspan Corporation Method for the initiation of chemical reactions by low pressure optical pumping
US4158589A (en) * 1977-12-30 1979-06-19 International Business Machines Corporation Negative ion extractor for a plasma etching apparatus
US4293769A (en) * 1978-01-13 1981-10-06 Massachusetts Institute Of Technology Detecting IR and mm radiation
US4568436A (en) * 1982-08-25 1986-02-04 Westinghouse Electric Corp. Separation of isotopes of zirconium
US4496445A (en) * 1982-09-07 1985-01-29 Westinghouse Electric Corp. Separation of isotopes of zirconium
US4490225A (en) * 1982-09-07 1984-12-25 Westinghouse Electric Corp. Separation of isotopes of zirconium
US4634864A (en) * 1983-10-27 1987-01-06 Atom Sciences, Inc. Ultrasensitive method for measuring isotope abundance ratios
US4734579A (en) * 1983-10-27 1988-03-29 Atom Sciences, Inc. Ultrasensitive method for measuring isotope abundance ratios
US4654183A (en) * 1984-02-13 1987-03-31 The United States Of America As Represented By The United States Department Of Energy Production of intense negative hydrogen beams with polarized nuclei by selective neutralization of negative ions
US4786478A (en) * 1984-07-26 1988-11-22 Conoco Inc. Method and apparatus for isotope separation
US4704197A (en) * 1986-11-13 1987-11-03 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Isotope separation using tuned laser and electron beam
US4893019A (en) * 1987-05-27 1990-01-09 Mitsubishi Denki Kabushiki Kaisha Ion current generator system for thin film formation, ion implantation, etching and sputtering
US5011584A (en) * 1988-09-01 1991-04-30 Ultra-Centrifuge Nederland N.V. Method for separating a predetermined isotope of an element from a gaseous compound containing said element
US5115135A (en) * 1989-04-21 1992-05-19 Mitsubishi Denki Kabushiki Kaisha Ion source
US5110562A (en) * 1989-08-04 1992-05-05 Doryokuro Kakunenryo Kaihatsu Jigyodan Laser isotope separation apparatus
WO1993003826A1 (en) * 1991-08-14 1993-03-04 United States Department Of Energy Gadolinium photoionization process
US5202005A (en) * 1991-08-14 1993-04-13 The United States Of America As Represented By The United States Department Of Energy Gadolinium photoionization process
WO1997012373A3 (en) * 1995-09-15 1997-05-09 British Nuclear Fuels Plc Method and apparatus for laser separation of molecular compounds
WO2002014938A1 (en) * 2000-08-15 2002-02-21 Accelight Investments, Inc. High speed polarization mode dispersion compensator
WO2008122205A1 (fr) * 2007-04-06 2008-10-16 Peking University Procédé pour accélérer des ions au moyen d'un laser et appareil pour générer des ions
WO2016109842A1 (en) * 2015-01-02 2016-07-07 Board Of Regents Efficiently ionizing atoms based on electron excitation
US11307129B2 (en) 2020-03-23 2022-04-19 Savannah River Nuclear Solutions, Llc Automatic gas sorption apparatus and method

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FR2315310B1 (ref) 1982-11-12
FR2315310A1 (fr) 1977-01-21
CA1061476A (en) 1979-08-28
GB1534909A (en) 1978-12-06

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